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<H1 class="no-header">scr_dump 5 2025-01-18 ncurses 6.5 File formats</H1>
<PRE>
<STRONG><A HREF="scr_dump.5.html">scr_dump(5)</A></STRONG>                      File formats                      <STRONG><A HREF="scr_dump.5.html">scr_dump(5)</A></STRONG>




</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
       scr_dump - <EM>curses</EM> screen dump


</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
       The  curses library provides applications with the ability to write the
       contents of a window to an external file using <STRONG>scr_dump</STRONG> or <STRONG>putwin</STRONG>,  and
       read it back using <STRONG>scr_restore</STRONG> or <STRONG>getwin</STRONG>.

       The  <STRONG>putwin</STRONG>  and  <STRONG>getwin</STRONG>  functions  do  the  work;  while <STRONG>scr_dump</STRONG> and
       <STRONG>scr_restore</STRONG> conveniently save  and  restore  the  whole  screen,  i.e.,
       <STRONG>stdscr</STRONG>.


</PRE><H3><a name="h3-ncurses6">ncurses6</a></H3><PRE>
       A  longstanding implementation of screen-dump was revised with ncurses6
       to remedy problems with the earlier approach:

       <STRONG>o</STRONG>   A "magic number" is written to the  beginning  of  the  dump  file,
           allowing  applications  (such  as <STRONG>file(1)</STRONG>) to recognize curses dump
           files.

           Because ncurses6 uses a new  format,  that  requires  a  new  magic
           number  was  unused  by other applications.  This 16-bit number was
           unused:

               0x8888 (octal "\210\210")

           but to be more certain, this 32-bit number was chosen:

               0x88888888 (octal "\210\210\210\210")

           This is the pattern  submitted  to  the  maintainers  of  the  <STRONG>file</STRONG>
           program:

               #
               # ncurses5 (and before) did not use a magic number,
               # making screen dumps "data".
               #
               # ncurses6 (2015) uses this format, ignoring byte-order
               0    string    \210\210\210\210ncurses    ncurses6 screen image
               #

       <STRONG>o</STRONG>   The screen dumps are written in textual form, so that internal data
           sizes are not directly related to the dump-format, and enabling the
           library  to  read  dumps  from  either  narrow-  or wide-character-
           configurations.

           The  <EM>narrow</EM>  library  configuration  holds  characters  and   video
           attributes  in  a  32-bit  <STRONG>chtype</STRONG>, while the <EM>wide-character</EM> library
           stores this information in the <STRONG>cchar_t</STRONG>  structure,  which  is  much
           larger than 32-bits.

       <STRONG>o</STRONG>   It  is  possible  to  read  a  screen  dump  into a terminal with a
           different screen-size, because the library truncates or  fills  the
           screen as necessary.

       <STRONG>o</STRONG>   The ncurses6 <STRONG>getwin</STRONG> reads the legacy screen dumps from ncurses5.


</PRE><H3><a name="h3-ncurses5-_Legacy_">ncurses5 (Legacy)</a></H3><PRE>
       The screen-dump feature was added to <EM>ncurses</EM> in June 1995.  While there
       were fixes and improvements in succeeding years, the basic  scheme  was
       unchanged:

       <STRONG>o</STRONG>   The <EM>WINDOW</EM> structure was written in binary form.

       <STRONG>o</STRONG>   The <EM>WINDOW</EM> structure refers to lines of data, which were written as
           an array of binary data following the <EM>WINDOW</EM>.

       <STRONG>o</STRONG>   When <STRONG>getwin</STRONG> restored the window, it would  keep  track  of  offsets
           into  the  array of line-data and adjust the <EM>WINDOW</EM> structure which
           was read back into memory.

       This is similar to Unix System V, but does not write a  "magic  number"
       to identify the file format.


</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
       There is no standard format for <EM>curses</EM> screen dumps.  A brief survey of
       the existing implementations follows.


</PRE><H3><a name="h3-X_Open-Curses">X/Open Curses</a></H3><PRE>
       X/Open Curses Issue 7 specifies little.   It  says  (boldface  emphasis
       added)

          "[t]he  <EM>getwin()</EM>  function  reads  window-related data stored in the
          file by <EM>putwin()</EM>.  The function then creates and initializes  a  new
          window using that data.

          The  <EM>putwin()</EM>  function writes all data associated with <EM>win</EM> into the
          <EM>stdio</EM> stream to which <EM>filep</EM> points,  using  an  <STRONG>unspecified</STRONG>  <STRONG>format</STRONG>.
          This information can be retrieved later using <EM>getwin()</EM>."

       In  the  mid-1990s  when  the X/Open Curses document was written, there
       were still System V systems using older, less capable <EM>curses</EM> libraries.
       BSD  <EM>curses</EM>  was  not  relevant  to  X/Open because it did not meet the
       criteria for base-level conformance; see <STRONG><A HREF="ncurses.3x.html">ncurses(3x)</A></STRONG>.


</PRE><H3><a name="h3-System-V">System V</a></H3><PRE>
       System V <EM>curses</EM> identified the file format by writing a "magic  number"
       at  the  beginning  of the dump.  The <EM>WINDOW</EM> data and the lines of text
       follow, all in binary form.

       Solaris <EM>curses</EM> has the following definitions.

           /* terminfo magic number */
           #define MAGNUM  0432

           /* curses screen dump magic number */
           #define SVR2_DUMP_MAGIC_NUMBER  0433
           #define SVR3_DUMP_MAGIC_NUMBER  0434

       That is, the feature was likely introduced in SVr2 (1984), and improved
       in  SVr3  (1987).   Solaris <EM>curses</EM> has no magic number for SVr4 (1989).
       Other System V operating systems (AIX and HP-UX)  use  a  magic  number
       that would correspond to the following.

           /* curses screen dump magic number */
           #define SVR4_DUMP_MAGIC_NUMBER  0435

       That  octal  number in bytes is 001, 035.  Because most Unix vendors at
       the time used big-endian hardware, the magic number is written with the
       high-order byte first.

           \001\035

       After  the magic number, the <EM>WINDOW</EM> structure and line data are written
       in binary format.  While the magic number used by these systems can  be
       observed  with <STRONG>od(1)</STRONG>, none of them documents the format used for screen
       dumps.

       Nor do they use an identical format, even  with  the  System V  family.
       The <EM>ncurses</EM> <EM>savescreen</EM> test program was used to collect information for
       this manual page.  It produced dumps of different size (all  on  64-bit
       hardware, on 40x80 screens):

       <STRONG>o</STRONG>   AIX (51817 bytes)

       <STRONG>o</STRONG>   HP-UX (90093 bytes)

       <STRONG>o</STRONG>   Solaris 10 (13273 bytes)

       <STRONG>o</STRONG>   <EM>ncurses</EM>5 (12888 bytes)


</PRE><H3><a name="h3-Solaris">Solaris</a></H3><PRE>
       As  noted  above,  Solaris  <EM>curses</EM> has no magic number corresponding to
       SVr4 <EM>curses</EM>.  This is odd, since Solaris was the first operating system
       to meet the SVr4 guidelines.  Solaris furthermore supplies two versions
       of <EM>curses</EM>.

       <STRONG>o</STRONG>   The default <EM>curses</EM> library uses the SVr3 magic number.

       <STRONG>o</STRONG>   An alternate <EM>curses</EM> library (which we term <EM>xcurses),</EM>  available  in
           <EM>/usr/xpg4</EM>, uses a textual format with no magic number.

           According  to  its  copyright  notice,  this  <EM>xcurses</EM>  library  was
           developed by MKS (Mortice Kern Systems) from 1990 to 1995.

           Like ncurses6,  it  includes  a  header  with  parameters.   Unlike
           ncurses6,  the  contents  of the window are written piecemeal, with
           coordinates and attributes for  each  chunk  of  text  rather  than
           writing the whole window from top to bottom.


</PRE><H3><a name="h3-PDCurses">PDCurses</a></H3><PRE>
       <EM>PDCurses</EM>  added  support  for screen dumps in version 2.7 (2005).  Like
       System V and ncurses5, it writes the <EM>WINDOW</EM> structure  in  binary,  but
       begins  the  file  with  its three-byte identifier "PDC", followed by a
       single-byte version number.

                "PDC\001"


</PRE><H3><a name="h3-NetBSD">NetBSD</a></H3><PRE>
       As  of  April  2017,  NetBSD  <EM>curses</EM>  does  not  support  <STRONG>scr_dump</STRONG>  and
       <STRONG>scr_restore</STRONG> (or <STRONG>scr_init</STRONG>, <STRONG>scr_set</STRONG>), although it has <STRONG>putwin</STRONG> and <STRONG>getwin</STRONG>.

       Like  ncurses5, NetBSD <STRONG>putwin</STRONG> does not identify its dumps with a useful
       magic number.  It writes

       <STRONG>o</STRONG>   the <EM>curses</EM> shared library major and minor versions as the first two
           bytes (for example, 7 and 1),

       <STRONG>o</STRONG>   followed by a binary dump of the <EM>WINDOW</EM>,

       <STRONG>o</STRONG>   some  data  for wide characters referenced by the <EM>WINDOW</EM> structure,
           and

       <STRONG>o</STRONG>   finally, lines as done by other implementations.


</PRE><H2><a name="h2-EXAMPLES">EXAMPLES</a></H2><PRE>
       Given a simple program which writes text to the  screen  (and  for  the
       sake of example, limiting the screen-size to 10x20):

           #include &lt;curses.h&gt;

           int
           main(void)
           {
               putenv("LINES=10");
               putenv("COLUMNS=20");
               initscr();
               start_color();
               init_pair(1, COLOR_WHITE, COLOR_BLUE);
               init_pair(2, COLOR_RED, COLOR_BLACK);
               bkgd(<STRONG>COLOR_PAIR(1)</STRONG>);
               move(4, 5);
               attron(A_BOLD);
               addstr("Hello");
               move(5, 5);
               attroff(A_BOLD);
               attrset(A_REVERSE | <STRONG>COLOR_PAIR(2)</STRONG>);
               addstr("World!");
               refresh();
               scr_dump("foo.out");
               endwin();
               return 0;
           }

       When run using ncurses6, the output looks like this:

           \210\210\210\210ncurses 6.0.20170415
           _cury=5
           _curx=11
           _maxy=9
           _maxx=19
           _flags=14
           _attrs=\{REVERSE|C2}
           flag=_idcok
           _delay=-1
           _regbottom=9
           _bkgrnd=\{NORMAL|C1}\s
           rows:
           1:\{NORMAL|C1}\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
           2:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
           3:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
           4:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
           5:\s\s\s\s\s\{BOLD}Hello\{NORMAL}\s\s\s\s\s\s\s\s\s\s
           6:\s\s\s\s\s\{REVERSE|C2}World!\{NORMAL|C1}\s\s\s\s\s\s\s\s\s
           7:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
           8:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
           9:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s
           10:\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s\s

       The first four octal escapes are actually nonprinting characters, while
       the remainder of the file is printable text.  You may notice:

       <STRONG>o</STRONG>   The actual color pair values are not written to the file.

       <STRONG>o</STRONG>   All characters are shown in printable  form;  spaces  are  "\s"  to
           ensure they are not overlooked.

       <STRONG>o</STRONG>   Attributes  are  written  in escaped curly braces, e.g., "\{BOLD}",
           and may include a color pair (C1 or C2 in this example).

       <STRONG>o</STRONG>   The parameters in the header are  written  out  only  if  they  are
           nonzero.  When reading back, order does not matter.

       Running the same program with Solaris <EM>xpg4</EM> curses gives this dump:

           MAX=10,20
           BEG=0,0
           SCROLL=0,10
           VMIN=1
           VTIME=0
           FLAGS=0x1000
           FG=0,0
           BG=0,0,
           0,0,0,1,
           0,19,0,0,
           1,0,0,1,
           1,19,0,0,
           2,0,0,1,
           2,19,0,0,
           3,0,0,1,
           3,19,0,0,
           4,0,0,1,
           4,5,0x20,0,Hello
           4,10,0,1,
           4,19,0,0,
           5,0,0,1,
           5,5,0x4,2,World!
           5,11,0,1,
           5,19,0,0,
           6,0,0,1,
           6,19,0,0,
           7,0,0,1,
           7,19,0,0,
           8,0,0,1,
           8,19,0,0,
           9,0,0,1,
           9,19,0,0,
           CUR=11,5

       Solaris  <STRONG>getwin</STRONG>  requires  that  all parameters are present, and in the
       same order.  The <EM>xpg4</EM> curses library does not know about the <STRONG>bce</STRONG>  (back
       color erase) capability, and does not color the window background.

       On  the  other  hand,  the  SVr4  curses  library  does  know about the
       background color.  However, its screen dumps are in  binary.   Here  is
       the corresponding dump (using "od -t x1"):

           0000000 1c 01 c3 d6 f3 58 05 00 0b 00 0a 00 14 00 00 00
           0000020 00 00 02 00 00 00 00 00 00 00 00 00 00 00 00 00
           0000040 00 00 b8 1a 06 08 cc 1a 06 08 00 00 09 00 10 00
           0000060 00 00 00 80 00 00 20 00 00 00 ff ff ff ff 00 00
           0000100 ff ff ff ff 00 00 00 00 20 80 00 00 20 80 00 00
           0000120 20 80 00 00 20 80 00 00 20 80 00 00 20 80 00 00
           *
           0000620 20 80 00 00 20 80 00 00 20 80 00 00 48 80 00 04
           0000640 65 80 00 04 6c 80 00 04 6c 80 00 04 6f 80 00 04
           0000660 20 80 00 00 20 80 00 00 20 80 00 00 20 80 00 00
           *
           0000740 20 80 00 00 20 80 00 00 20 80 00 00 57 00 81 00
           0000760 6f 00 81 00 72 00 81 00 6c 00 81 00 64 00 81 00
           0001000 21 00 81 00 20 80 00 00 20 80 00 00 20 80 00 00
           0001020 20 80 00 00 20 80 00 00 20 80 00 00 20 80 00 00
           *
           0001540 20 80 00 00 20 80 00 00 00 00 f6 d1 01 00 f6 d1
           0001560 08 00 00 00 40 00 00 00 00 00 00 00 00 00 00 07
           0001600 00 04 00 01 00 01 00 00 00 01 00 00 00 00 00 00
           0001620 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
           *
           0002371


</PRE><H2><a name="h2-AUTHORS">AUTHORS</a></H2><PRE>
       Thomas E. Dickey
       extended screen-dump format for <EM>ncurses</EM> 6.0 (2015)

       Eric S. Raymond
       screen dump feature in <EM>ncurses</EM> 1.9.2d (1995)


</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
       <STRONG><A HREF="curs_scr_dump.3x.html">curs_scr_dump(3x)</A></STRONG>, <STRONG><A HREF="curs_util.3x.html">curs_util(3x)</A></STRONG>



ncurses 6.5                       2025-01-18                       <STRONG><A HREF="scr_dump.5.html">scr_dump(5)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a href="#h3-ncurses6">ncurses6</a></li>
<li><a href="#h3-ncurses5-_Legacy_">ncurses5 (Legacy)</a></li>
</ul>
</li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a>
<ul>
<li><a href="#h3-X_Open-Curses">X/Open Curses</a></li>
<li><a href="#h3-System-V">System V</a></li>
<li><a href="#h3-Solaris">Solaris</a></li>
<li><a href="#h3-PDCurses">PDCurses</a></li>
<li><a href="#h3-NetBSD">NetBSD</a></li>
</ul>
</li>
<li><a href="#h2-EXAMPLES">EXAMPLES</a></li>
<li><a href="#h2-AUTHORS">AUTHORS</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
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